Ever increasing concerns over pollutants within the environment, require improved monitoring and/or analysis for the detection of certain chemical species, e.g., organic compounds such as benzene. While analytical techniques are available to detect the presence of many substances down to levels as low as parts per billion or less, such analytical techniques generally require collecting a sample in the field, taking the sample to a laboratory, and analyzing the sample by, e.g., gas chromatography or mass spectroscopy. Such analysis requires sophisticated equipment that generally requires up to several days to obtain final results and such analysis is not generally suited to use in the field. Thus, present anayltical techniques fail to provide any real time information about the presence of pollutants or contaminants.
In an effort to overcome the limitations of present anaytlical techniques, much research has been directed to developing chemical sensors that can give more rapid feedback information. One example of such a chemical sensor is found in U.S. Pat. No. 5,151,110 wherein a sensor includes a piezoelectric substrate, preferably contained within a surface acoustic wave (SAW) device or a quartz crystal microbalance (QCM) device, and a coating, such as zeolite crystals in an inorganic silica matrix, applied to the substrate to selectively sorb chemical entities of a size less than a predetermined magnitude. While such a chemical sensor is useful, it is limited to materials that physically fit within the particular pore sizes of the zeolite crystals. Additionally, as the selective layer including the zeolite crystals and a polymeric binder material are coated onto the substrate by conventional coating techniques such as dip-coating, spraying, spin-coating and the like, the selective layer is subject to durability problems such as separation from the substrate due to poor adhesion.
U.S. Pat. No. 4,860,573 desribes a composite substrate intended for an apparatus for quantitative detection of, e.g., an organic component present in a gas or liquid. Cyclodextrin is described as one material for incorporation as an active site material into the composite substrate. However, there is no teaching or suggestion of multilayers of the active site material, nor is there any teaching or suggestion of using cyclodextrin derivatives or of forming oriented cycxlodextrin derivative structures by the controlled assembly of such materials.
It is an object of the present invention to provide a chemical sensor including a cyclodextrin derivative and a method of detecting chemical pollutants or contaminants, preferably in an on-site, real time process.
It is a further object of the invention to provide a chemical sensor, including a cyclodextrin derivative, having sensitivity to detect low levels of selected chemical pollutants or contaminants.
It is a still further object of the invention to provide a reversible chemical sensor including a cyclodextrin derivative.
Yet another object of the invention is to provide a chemical separator including a cyclodextrin derivative for reversibly separating selected chemical species.